1. Field of the Invention
This invention relates to an apparatus for cutting excavations having a substantially planar face. The apparatus comprises a cutting tool rotatably mounted on a jib, which is pivoted to a mobile machine.
2. Description of the Prior Art
In conventional cutting machines, the jib or cutter arm is pivoted on a chassis for rotation about a substantially vertical axis and about a substantially horizontal axis. The jib must be long enough to permit the making of excavations having a relatively large cross-sectional area but the pivotal movement of such jib in a lateral or vertical direction will result in the formation of a substantially curved face. If the roof tends to cave in, the road must be provided with temporary supports close to the working face in order to prevent the roof from breaking down. The placing of such temporary supports is relatively expensive and time-consuming and the temporary supports cannot be placed as close as possible to the working face because the cutter arm or jib is pivotally movable also in a lateral direction. Besides, the use of such temporary supports gives rise to a need for expensive means by which the supporting frames and auxiliary means required for the placing of the supports can be moved over the cutting machines disposed at the working face, and the space close to the working face is relatively confined. In the use of the known apparatus, the cutting work must be interrupted for the placing of supports close to the working face because it is not possible to provide a reliable guard at locations disposed between the cutting tools and close to the working face as such guards would be struck by the cutter arm.